The present invention relates to a high frequency cable and a high frequency coil, and particularly to a high frequency cable used as a winding wire, a litz wire, a cable and the like for various high frequency devices, and to a high frequency coil.
In winding wires and feed cables of devices (such as a transformer, a motor, a reactor, induction heating equipment, a magnetic head assembly) in which a high frequency current flows, eddy-current losses are caused in conductors due to magnetic fields generated by the high frequency currents, and, as a result, alternating-current resistance is increased (skin effect and proximity effect are enhanced), thus causing heat generation and an increase in power consumption. As a general measure to suppress enhancement of skin effect and proximity effect, a reduction of wire diameter and use of litz wire in which each wire has insulating coating are adapted (for example, refer to Japanese Unexamined Patent Application Publication No 2009-129550 (hereinafter referred to as “Patent Literature 1”), Japanese Unexamined Patent Application Publication No. Showa 62-76216 (hereinafter referred to as “Patent Literature 2”), Japanese Unexamined Patent Application Publication No. 2005-108654 (hereinafter referred to as “Patent Literature 3”), International Publication No. WO2006/046358 (hereinafter referred to as “Patent Literature 4”) and Japanese Unexamined Patent Application Publication No. 2002-150633 (hereinafter referred to as “Patent Literature 5”)).
However, with the means of the prior art, it is difficult to remove the insulating thin layer during a soldering process for the conductor connection, and there is a limit to wire diameter reduction because the number of wires increases. In addition, no effective measures have been found to suppress proximity effect for wires having diameters with which proximity effect is overwhelmingly predominant compared to skin effect, and it is commonly known that characteristics obtained by the diameter reduction measure have limitation. Although examples of countermeasures are presented in Patent Literatures 1 to 5, all of those countermeasures are ideas only and short on specifics, and cannot be regarded as effective countermeasures.
Moreover, in Patent Literature 2, a plurality of composite conductors made from a central conductor and an outer conductor are twisted together and recrystallized through a thermal treatment to manufacture a high frequency cable. However, with this cable, it is difficult to sufficiently suppress proximity effect, and damage and deformation occur easily during manufacturing processes, so it has been difficult to sufficiently stabilize the characteristics of the cable as a coil.